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Full text of "Outdoors"

Catapult Glider Launcher 



Make] Projects 

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build, hack, tweak, share, discover,- 



Catapult Glider Launcher 

Written By: Rick Schertle 



TOOLS: 



PARTS: 



• Drill and drill bits (1) 
Hacksaw (1) 
Miter saw (1) 
Scissors (1) 

Screwdriver and wrench (1) 
Wire cutter/stripper (1) 



Lumber (1) 

Cheap pine is fine: I used clear fir for a 

nicer look. 

Bolts (1) 

Nuts (8) 

Wing nuts (2) 

Washers (20) 

Wood screws (1) 

Screw eyes (4) 

Chain (1) 

Wood glue (1) 

Hinge. T style (1) 

Aluminum C-channel (1) 

Surgical tubing (1) 

Steel rodJU 

Wire or cable (1) 

Rubber band (1) 

or you can double a 7" band 

Roped) 



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Page 1 of 10 



Catapult Glider Launcher 

needs to slip smoothly through screw 
eyes 

Wire clothes hangers (1) 

• Folding-wing glider (1) 

for launching. Make your own at 
makeprojects.eom/project/f/ 1934, or get 
our Rocket Glider kit item #MKRS2 at 
Maker Shed (makershed.com). 



SUMMARY 

For many years, the U.S. military has enjoyed playing with "toys." 

Today that includes unmanned drone aircraft, but in the past, it was toy balsa wood 
airplanes. Thousands of folding-wing balsa gliders were shot out of the sky in the early 
1940s for World War II artillery practice. High in the air, these toy airplanes had the scale 
effect of a full-sized plane. Developed and patented in 1939 by Jim Walker, founder of the 
American Junior Aircraft Company, the folding-wing Army Interceptor glider bore the brunt of 
the action. 

My folding-wing Rocket Glider , based on the Interceptor, was featured as a how-to project in 
MAKE Volume 31 and is available as a kit from Maker Shed . While the Interceptor originally 
used a handheld rubber-band catapult, the military designed a launcher to hurl the gliders 
nearly 300 feet high. In 2004, Frank Macy designed the first reproduction of this launcher, on 
which this project is based. 

With nearly 20 pounds of pulling force, this simple catapult remarkably flings the tiny glider 
(weighing less than an ounce) 150 feet into the air. Stand clear, pull the rope trigger, and 
watch a piece of history rocket into the sky! 



© Make Projects www.makeprojects.com Page 2 of 1 



Catapult Glider Launcher 



Step 1 — Build the tripod catapult stand. 




W hole 
: or rubber 
tubing; all 
other 

holes Va" 



Catapult arms are lx2's. 
All legs are 8 T long 2x2*s. 



IZW 



141 



Rear leg 

of tripod 



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I. ' '\H — 1*2*12" 



« j , -1-1x2x16" 



2x2x38" E 




• Cut the lumber to the following lengths: 

• 2x2:8' (3), 38" (1), and 47" (1) 

• 1x2: 36" (2), 12" (1), 16" (1), 17" (1), and 3" (1) 

• 1x4: 30" (1) 



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Catapult Glider Launcher 



Step 2 





• Assemble the tripod stand, following the assembly drawings (Step 1). Cut the top inside 
corners of the 2 front legs at 15° so they'll meet the rear leg flush when they're splayed 
out. 

• Drill 1/4" holes where indicated, then attach the pieces with 1/4" bolts, washers, and nuts, 
except the 30" launch platform (see Step 3). 

• Use wing nuts at the top of the tripod (with a 4" bolt) and where the catapult arms attach to 
the rear leg (5-1/2" bolt). This way, the catapult arms can be loosened and swung back so 
the launcher is more portable. 

• Attach one screw eye 3' up on the rear leg, and another on the upper rail that supports the 
launch platform. Measure 33" of chain and attach it to both screw eyes. 

• Drill 1/2" holes horizontally through the free ends of the catapult arms. 



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Catapult Glider Launcher 



Step 3 — Build the launch platform. 



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• Cut the aluminum C-channel to 26" using a hacksaw. Following the diagram, place the 
channel, open side up, in the center of the 1 x4 board, 2" from the top. Drill pilot holes 
through the channel and attach it with 3/4" wood screws. 

• Measure down 14-1/4" from the top of the 1 x4, then drill two 1/4" holes 1-1/2" apart (on 
center), one on each side of the channel. 

• To install the wing holder, cut a 10" piece of wire from a clothes hanger and bend it into the 
shape shown in the photo. Then screw it into the launch platform 8-1/4" below the 1/4" 
holes you made. Placement is important; it must hold the Rocket Glider's wings back, but 
not impede it from leaving the launcher. 

• If you'll be launching some other craft, don't install the wing holder yet; wait until you build 
the trigger mechanism in the next step so you can get your measurements right. 

• Attach a screw eye centered in the bottom edge of the launch platform; this will guide the 
trigger cord. 

• Finally, mount the launch platform centered on the lower horizontal rails on the tripod 
stand, using wood screws. 



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Catapult Glider Launcher 



Step 4 — Make the trigger. 






• Glue and screw the 3" piece of 1 x2 horizontally to the top of the 17" piece of 1 x2. Drill two 
3/32" or 1/8" holes in the horizontal piece, 1-1/2" apart, so the 1/8" rod will fit snugly. 

• Bend the 1/8" rod into a U shape with 4" legs, 1-1/2" wide at the base. Carefully hammer 
the U-shaped rod all the way into the 2 holes so they stick out the other side about 3". 
These are the trigger rods. 

• Drill a 1/2" hole through the bottom of the trigger board and tie the launch cord through it. 

• IMPORTANT: Make sure the trigger rods are the same length, so they'll release the 
glider at the same time. 



it 



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Catapult Glider Launcher 



Step 5 — Put it all together. 









• Feed the trigger rods through the 1/4" holes in the launch platform. Attach 2 wood screws 
into the sides of the launch platform and stretch a rubber band between them to hold the 
trigger board in place. The 2 pins should move easily in and out of the holes in the launch 
platform. Bend them if you need to. 

• When you're satisfied with the trigger action, attach the T-hinge to the trigger board and 
the bottom rail. 

• Feed the trigger cord through the screw eye in the bottom of the launch platform. 

• Cut the surgical tubing into two 3' lengths and tie a big knot in one end of each. Feed these 
through the 1/2" holes in the ends of the catapult arms. 

• Cut a 24" length of the heavy coated wire and tie a knot in each end. Tie the wire into the 
free ends of each length of surgical tubing. You're done. 



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Catapult Glider Launcher 



Step 6 — Launching tips 



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Catapult Glider Launcher 




• Set up your launcher on a good- 
sized field with little or no wind. 
With the catapult arms in launch 
position, tighten the wing nuts. 

• Pull the surgical tubing downward 
and hook the catapult wire onto the 
trigger rods. The tubing should be 
pointing straight up vertically. 

• Now practice triggering the catapult 
without the glider. With your head 
well clear, place one foot on the 
catapult cross-rail, and slowly pull 
the rope back, triggering the 
catapult. Don't jerk it, or the trigger 
can bounce back and damage your 
glider. 

• This is an extremely powerful 
catapult to launch a glider that 
weighs barely 1oz. There is room 
for disaster. I suggest practice- 
launching something else before 
you move on to the glider. 

• Now for the true test. With the 
wings folded back, place the glider 
in the C-channel, and hook the 
launch notch in the bottom of the 
glider onto the catapult wire. The 
folded wings should slip freely into 
the wire wing holder. 

• Just like the U.S. Army did 70 
years ago with a similar launcher, 
pull the rope slowly ... and watch 
your glider zip skyward. 



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Page 9 of 1 



Catapult Glider Launcher 
Mods 

This catapult launcher is a rough replica of the one used by the U.S. military, so while it folds, 
it's still not very portable. I challenge MAKE readers to come up with more compact and clever 
designs and share them here. The possibilities are endless! 

This project first appeared in MAKE Volume 32 , page 104. 

This document was last generated on 201 2-1 0-30 08:1 6:47 PM. 



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